Physical and Chemical Changes

Physical Property

Observable traits that do not change the identity of the substance

Include color, shape, smell, taste, mass, volume and density

Also include ductility, malleability, conductivity and solubility

Can be determined without changing a substance

Physical Property

Density - mass/volume Ductility – ability to be pulled into wire

Malleability – ability to be hammered

Conductivity – ability to pass electric current

Solubility – ability to dissolve

Physical Change

Any change in size, shape, form, or state where the identity of the matter stays the same

Ex. - Cutting a watermelon into slices

Often easy to reverse with filtration, magnetism, evaporation, distillation, and centrifuge

Physical Change

Evidence includes: same substance no new substances color change state change same smell, taste, texture different volume, mass same density

Chemical Property

The characteristic of a substance that allows it to change into something different

Includes flammability, reactivity with oxygen, and acidity

Testing for chemical properties causes a change in the substance

Chemical Property

Flammability – able to be burned; combustion

Reactivity with oxygen Acidity

pH level scale from 1 to 14 1 being most acidic 14 being least acidic (most basic) Water is a 7 (neutral) on the pH scale

Chemical Change

Happens when a substance undergoes a change that causes it traits to change

Ex. - digestion, photosynthesis, paint drying, and oil burning.

New materials are formed that are different from the starting materials

Chemical Change

NOT easily reversed Evidence includes:

Release of energy – light, heat, sound

Formation of gas or solid that is NOT the results of simple state change

Chemical Change

Evidence includes: new substance

Example of Chemical Change

Chlorine Added to swimming pools and drinking water

Causes acidity Prevents reproduction, growth and development of algae, bacteria, protists and insects.

Types of Chemical Reactions

Synthesis Decomposition

Acids and Bases

Acids Sharp smell, sour taste Corrode metals, harmful to organisms pH between 0 and 7 Ex. - citrus fruits contain acids.

Bases Feel slippery, taste bitter May also be harmful to organisms pH of between 7 and 14 Ex. - a bar of soap is basic

Salts

Salts are compounds of metal and nonmetal

Formed when acids and bases react

Ex. – table salt and chalk

Energy…

…is required for both types of changes